TRAVERSE CITY, Mich.  Known as Pigeon Hill, the Lake Michigan dune towered 30 stories high on the south side of Muskegon. Formed over thousands of years, it disappeared in three decades as its sand was mined for industrial use in the mid-20th century.

"You can only see Pigeon Hill in a museum now," said Tanya Cabala, an environmental consultant from Whitehall who has studied its history.

Michigan has regulated sand mining since then, although environmentalists want stronger controls. But Great Lakes dunes also face other threats, from invasive plant species to abuse by all-terrain vehicles, scientists and government officials said Tuesday.

During a conference funded by the Environmental Protection Agency, experts agreed to seek a regionwide strategy for protecting the ecologically unique chain of dunes stretching along many of the lakes' coastlines.

"These are truly world-class, fantastic dunes," said Alan Arbogast, associate professor of geography at Michigan State University. "We have good reason to love these dunes."

Their value goes beyond aesthetics, said Karen Rodriguez, a specialist with the EPA's Great Lakes National Program Office. The dunes provide habitat for rare native plants and animals, such as the piping plover and the Pitcher's thistle. And they shelter other important geological features, such as coastal wetlands.

While scientists have studied dunes in specific areas, they lack comprehensive data on the entire Great Lakes regional network, Rodriguez said. That's one reason the EPA approved a request from the New York Sea Grant program to fund the conference.

It's uncertain how many acres of dunes exist and where all of them are, she said. Also needed is a means of analyzing their ecological health.

"We don't have a baseline; we don't know where the system is going," Rodriguez said.

A goal of the conference is to establish a regional coalition that will work cooperatively to protect the dunes, said Mark Breederland, an extension educator with Michigan Sea Grant.

The eight states and two Canadian provinces adjoining the lakes also should compare notes on management policies as they try to protect the dunes while accommodating people who use them for beach access, hiking, bird-watching and other recreation, Rodriguez said.

Biologist J.P. Dech of Ontario's Nipissing University said his research at Pinery Provincial Park on Lake Huron turned up a variety of pressures on dunes, such as recreational use, climate change, deer browsing, storms and exotic species.

"It is possible to actually love something to death," said Jim Buchholz, a supervisor at Kohler-Andrae State Park in Sheboygan, Wis. The 1,000-acre park, an increasingly popular tourist attraction, features an unusual set of dunes intermingled with wetlands that are under attack by purple loosestrife.

Invasives also are a problem at Sleeping Bear Dunes National Lakeshore in northern Michigan, staff biologist Ken Hyde said. Plants such as baby's breath are replacing natural grasses that help stabilize dune sands, while knapweed hampers germination of native vegetation.

Managers of state and national parks said they were trying numerous methods to protect dunes, such as installing boardwalks to keep hikers from wandering off paths and installing signs to educate visitors about the areas' fragility.

Government budget cuts are forcing parks to call on volunteers for help in maintaining trails, removing invasive plants and other tasks, Buchholz said.

"It's certainly more of a challenge than it's ever been before to manage these places," he said.